Desorption studies of model contaminants from recycled PET in dry air and nitrogen atmosphere by thermogravimetric analysis

Abstract

The closed-loop recycling of PET bottles has to prove its ability to decontaminate recycled plastics into a level that offers a negligible risk to public health and does not compromise the organoleptic properties of packed foods. Our previous work [1] resulted in a new bottle-to-bottle process that employs dry air atmosphere under ideal mass and heat transfer conditions to remove contaminants from polymer matrix. The experimental results showed that dry air was able to increase the productivity of PET super-clean technologies, based on solid-state polymerization processes (SSP). In this work we have evaluated the difference in desorption rate of model contaminants from recycled PET in dry air and nitrogen atmosphere by thermogravimetric analysis. Furthermore, it was investigated if sample exposed to synthetic air and nitrogen atmosphere during the thermogravimetric analysis presented any difference in their thermal properties. According to the results obtained in this work, the thermogravimetric analysis was not sensitive to detect difference in the rate of contaminant desorption from PET in synthetic air and in nitrogen atmosphere and any evidence of interaction between PET matrix and exposed atmosphere has not been observed by DSC analysis.